Sexually conservative men are more swayed by sexual images than more adventurous dudes, according to a new study that might help explain why the sexually conservative, paradoxically, tend to take sexual risks.

The study suggests that men who have no intention of having casual sex nevertheless become more willing to do so after exposure to images of pretty women in bikinis. This willingness without intention may explain a lack of foresight that leads to sex without protection, the study researchers write today (June 19) in the British Journal of Health Psychology.

"Think of this as similar to young teenagers drinking," study researcher Megan Roberts, a psychologist at Brown University, said in a statement. "Most don't go out explicitly intending to get drunk, but are willing if they are offered alcohol at a party. Likewise, many adults do not intend to have casual sex, but would be willing to do so if presented with the opportunity." [50 Sultry Facts About Sex]

Studies dating back to the 1980s have found that people with conservative attitudes toward sex have less intercourse than the sexually liberal, as might be expected. But when the sexually conservative do get busy, they're more likely to take risks, such as not using protection against pregnancy or sexually transmitted infections.

A sexual mystery

This puzzle confused health researchers. To get the bottom of why people behave so strangely, Roberts and her colleagues first asked 75 college-age men if they intended to have casual sex with a stranger or acquaintance in the next six months. Twenty-eight of them (37 percent) said no.

The researchers then had the men do a word-identification task, into which the researchers had inserted subliminal images of either pretty bikini-clad women or neutral photographs, such as those showing lightening bolts. The images flashed onscreen for only 8 milliseconds, too few to register consciously.

After the subliminal image presentation, the men completed another questionnaire, this one including a vignette about going home with a woman from a party. The guys were asked how likely they were to engage in a variety of sexual acts with this near-stranger.

Intention versus willingness

The results confirmed that intention and willingness don't always go hand-in-hand. The men who said they had no intention of having casual sex became much more likely to report a willingness to do so — but only if they'd seen the subliminal sexy images. The guys who were already interested in casual sex weren't swayed by the images.

To confirm the findings, the researchers repeated the experiment with 112 men ages 18 to 57 recruited online. The only major difference in the second experiment was that the images weren't subliminal; instead, participants were told they were rating images for an ad campaign. Again, some saw sexy women, while others saw neutral photographs.

As in the first study, the sexually conservative became more willing to indulge in casual sex if they'd seen the bikini-clad hotties.

"Compared to men who intend to have casual sex, those who didn't showed an increase in willingness to do so if they had viewed sexual images," Roberts said. "This was even true for the older men who were in committed relationships. Overall, this suggests that sexually conservative men can be more swayed by subtle sexual cues."

The findings suggest that in the real world, the sexually conservative might not plan to have sex, Roberts and her colleagues wrote. When confronted with the opportunity, though, they might be relatively more swayed to do the deed than the sexually liberal — and because they haven't planned on having sex, they're probably less likely to be prepared with condoms or other protection.

Editor's Recommendations

Stephanie Pappas is a contributing writer for Live Science. She covers the world of human and animal behavior, as well as paleontology and other science topics. Stephanie has a Bachelor of Arts in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz. She has ducked under a glacier in Switzerland and poked hot lava with a stick in Hawaii. Stephanie hails from East Tennessee, the global center for salamander diversity. Follow Stephanie on Google+.